1. Field of the Invention
The present invention relates to a method and apparatus for non-contact deceleration of flat products, such as signatures or the like emerging from a folding apparatus.
2. State of the Art
U.S. Pat. No. 4,132,403 discloses a sheet-transfer apparatus for printing presses. Sheets are transferred from a supply to a continuously rotating receiver drum in a printing press by a transfer drum having at least two angularly spaced grippers. The drum carrying the grippers is rotated at a relatively slow speed, and each of the grippers can be angularly displaced on the transfer drum and relative to the other gripper. Thus, each gripper is accelerated after it has picked up a sheet at a pick-up station, so that when it reaches a transfer station where it passes the sheet off to the receiver drum, it is moving at the same speed as the receiver drum. Thereafter, each gripper is uniformly decelerated, so that when it has returned to the pick-up station, it is moving at the same speed as the sheet at the pick-up station.
U.S. Pat. No. 4,290,595 shows a rotatable advance, or forward, gripper drum. As described therein, a continuously rotatable advance gripper drum assembly is provided for sheet-fed rotary printing presses, and has an advance gripper drum and a gripper bridge movable relative to the drum. The gripper drum assembly includes a crank-driven linkage transmission device disposed on and rotatable with the advance gripper drum, and operatively connected to the gripper bridge for moving the gripper bridge.
U.S. Pat. No. 4,629,175 discloses a method and apparatus for the stream-feeding delivery of sheet-like products coming of a folder. The sheet-like products are initially transported some distance before being caused to overlap. In order to slow down the products for allowing this to take place, and to arrange them in a perfectly regular feeding stream without being damaged, the products are engaged by grippers which are moved along a preferably arcuate path on a support, in the course of which the products are slowed down by the grippers to the speed of a delivery belt whereon the products are then deposited.
U.S. Pat. No. 5,141,221 discloses a deceleration device in the folder of a rotary printing press. Folded products following one behind the other are gripped by decelerable transport devices and conveyed. The oppositely arranged transport devices tracing a path of motion are driven by a planetary gearing. While planetary gears rotate, an instantaneous center describes a cardioid which, via drive brackets, causes the transport devices to possess different speeds during rotation of the planetary gears.
U.S. Pat. No. 5,452,886 discloses a device for slowing down signatures in a folding apparatus. The device provides a plurality of rotary grippers which positively grip signatures exiting a tape-conveyor system in the folding apparatus traveling at a high velocity. A deceleration drum is also provided for slowing down the signatures through a smooth velocity profile. The deceleration drum has a plurality of pivot arms pivotally mounted on a pivot disc rotating about a first axis, the pivot arms being connected to a control disc by a control link, the control disc rotating about a second axis located parallel to and offset from the first axis. The rotary grippers are attached to outward ends of the pivot arms. The rotary grippers grip the leading edges of the signatures as they exit the tape-conveyor system while the trailing edges are still being controlled by the tape-conveyor system. The deceleration drum may alternately be constructed of a cam and linkage system in place of the pivot arm/pivot disk and a control link/control disk mechanism.
In practice, a technical problem has been encountered during deceleration of the signatures in the manner described by the foregoing patents, the disclosures of the '595 '175 '221 and '886 patents being incorporated herein by reference in their entireties. More particularly, the signature path of the trailing edges of the signatures during slow down follow essentially the same path as the leading edges of the signatures. As the paths are essentially identical, only friction due to the signature-buckling can be used to remove kinetic energy from the signatures moving with high speed before being slowed down. If the signature path is imposed on a deceleration drum, the signatures must be stiff enough to resist buckling when the leading edge of a signature is decelerated.